1. Field of the Invention
The invention relates to a tool for machining surfaces, in particular recesses, in bores of workpieces, having a tool wheel which is mounted in a rotatable manner on a holding arm and whose diameter exceeds the dimension of the holding arm transversely to the longitudinal direction of the same.
2. Description of the Related Art
DE 419 416 C discloses a grinding device having a turbine drive, in which grinding device the turbine wheels lie open for driving the grinding wheel, so that the drive medium discharges freely. Furthermore, the grinding wheel projects to a considerable extent on both sides of the holding arm, so that this holding arm, which is thin relative to the grinding-wheel diameter and in addition is also of fork-shaped design, does not have the necessary rigidity which is required for accurate machining. Furthermore, the open airflow or spray against the turbine blades limits the power transmission, for which reason a turbine of relatively large diameter is used, this turbine requiring an even larger grinding wheel, so that, during the machining of surfaces in bores, there are restrictions with regard to the inside diameter of these bores.
The object of the invention is to design a tool of the specified type in such a way that, at a relatively low design cost, small external dimensions for the machining inside small bores and relatively large chip-removing capacities can be achieved.
According to the invention, the tool wheel has a hollow tool-wheel carrier having an essentially rotationally symmetrical form and a machining body arranged on the outer periphery of the same, and the tool-wheel carrier together with a base body provided on the holding arm from a housing for accommodating the bearing arrangement and the drive for the tool wheel. The machining body projects beyond the outer dimension of the holding arm transversely to the longitudinal direction of the same only by slightly more than corresponds to the recess inside the bore of the workpiece, and the machining body projects beyond the holding arm only on one side of the latter.
The term xe2x80x9crecessxe2x80x9d refers to a groove or an internal thread.
The invention enables machining of longitudinal grooves in narrow bores, with an orientation of the grooves parallel to or at an angle to the bore axis, and the machining of thread turns, since this configuration offers compact external dimensions. Since the tool wheel is only slightly larger than corresponds to the dimension of the holding arm, the latter has high rigidity, as a result of which vibration-free machining of workpieces is possible. The interaction of the hollow rotationally symmetrical tool wheel with the base body of the holding arm creates a configuration which offers not only compact external dimensions but also protected arrangement of the bearing arrangements of the drive.
Since the tool wheel projects beyond the holding arm only on one side of the latter, especially narrow bores can be machined, since a clearance space between holder and inner bore is only required on the one side, at which the tool wheel projects beyond the holding arm.
The configuration of the tool wheel as a hollow rotationally symmetrical body provides the precondition for the machining body to be designed as an abrasive body or as a milling cutter.
An especially advantageous configuration with regard to achieving compact external dimensions is obtained if the tool-wheel carrier is of hemispherical or frustoconical design. This configuration is especially advantageous in combination with the design of the drive as a hydraulic drive, since in this way the space available can be utilized in an especially effective manner for the drive pails and also for the bearing parts.
Furthermore, it is advantageous if a projecting, bead-shaped abrasive-material support, which carries the abrasive material, is formed in one piece at the outer margin of the tool-wheel carrier, the abrasive-material support and abrasive material forming the machining body. This configuration leads in particular to a compact embodiment when, in a development of the invention, the tool-wheel carrier and the abrasive-material support are designed as a metal body, and the abrasive material is electrolytically applied to the abrasive-material support. The abrasive material may also be applied to the abrasive-material support by means of ceramic bonding, metallic bonding or synthetic resin bonding. The abrasive material may consist of cubic boron nitride or diamond. The metal body is preferably formed from steel. Such a tool provided as a grinding tool not only has compact external dimensions but also a very long service life on account of the abrasive material used.
When the grinding wheel or the milling cutter wears down, an exchange can easily be carried out on account of the configuration according to the invention, since in this case the tool-wheel carrier with the integrally formed machining body is connected as a unit to the remaining parts of the tool in an easily exchangeable manner.
A further simplification of the design is provided for by the base body being designed in one piece with the holding arm, which accommodates supply lines for the drive and/or the bearing arrangement.
If, in a further configuration of the invention, the bearing arrangement of the tool wheel is designed as a hydrodynamic bearing arrangement and the drive for the tool wheel is designed as a hydraulic drive, the oil required for the hydraulic drive may serve as lubricant for the hydrodynamic bearing arrangement of the tool wheel, a factor which reduces the design cost overall. With small dimensions, very high torques and thus high outputs can be transmitted to the tool wheel through the use of a hydraulic drive. Compared with the mechanical drives, the hydraulic drive for such a tool also has the advantage that, if the tool wheel stops suddenly, the drive cannot be damaged, as is the case in the mechanical drives on account of mass forces.
It is advantageous if the holding arm is provided with a tool-centering interface for securing to a machine tool, since the tool can be preset as a result.